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Runner in Motion

capture moving subjects with AI Servo AF

EOS 80D: Sophisticated AI Servo AF Control

By: Rudy Winston

April 04, 2016

We've highlighted how the EOS 80D is a great choice as a step-up camera in an earlier article on Canon USA’s Digital Learning Center. And, how that applies whether you’re an experienced DSLR user who’s working with an older camera, or a first-time but well-informed DSLR customer who’s looking to move beyond today’s lightweight, entry-level models.

Front view of Canon EOS 80D

The Canon EOS 80D (shown here with optional Battery Grip BG-E14) offers a compelling combination of performance and flexibility. This article explains how its AF system can be adjusted for different types of real-life action shooting situations.

One aspect of the advanced possibilities a camera like the EOS 80D offers is extensive fine-tuning and control of its continuous autofocus for moving subjects, called AI Servo AF. In a far less expensive package than Canon’s high-end models — such as the EOS 5D series or even the EOS-1D X models — the EOS 80D offers the action photographer a truly extensive array of in-camera adjustability and control. We’ll discuss what’s available in the EOS 80D in this article, and explain how it might be used in various real-world shooting situations.

Even if you’re not a prospective Canon EOS 80D customer at the moment, the points in this article may help you understand features and terminology you may have seen or heard discussed in the past, and perhaps didn’t have a complete grasp of. And, if you already own one of Canon’s higher-end models with these features, this may clarify points you can put into practice in your photography as well.

One other point: keep in mind that all these adjustments, and discussion of AI Servo AF in general in this article, refer to continuous autofocus when shooting through the viewfinder, using the camera’s 45-point AF system. Live View and video AF are performed very differently, assessing focus off the imaging sensor with Canon’s Dual Pixel AF technology.

EOS 80D’s 45-point AF system

Our comments about adjustment potential to the EOS 80D’s AF system refer to using the 45-point AF and viewing through the eye-level viewfinder. Whether you opt to work with one single AF point, as illustrated here, or expand the size of the AF Area, there are a number of tools to let you fine-tune how the AF system responds with different types of moving subjects. This article explores AI Servo AF’s adjustment potential in the EOS 80D.



What is AI Servo AF, and why would I want to adjust it?

First off, to be clear, AI Servo AF is Canon’s autofocus operation setting that allows the camera to continually focus upon moving subjects. It’s actually “AI” (letter “i,” as in ice cream), which stands for Artificial Intelligence. AI Servo AF not only lets the camera focus continually on moving subjects, but is able to begin to read a subject’s movement, and then predict its location when the shutter fires a split-second later — for each image you take. This is the “Artificial Intelligence” that the letters AI refer to.

AI Servo AF continually updates its focus information in-between each shot during a continuous sequence. Even at 7 frames per second, the camera takes a split-second between each shot, as the mirror returns to its normal viewing position, to re-assess focus, update the subject information, and drive the lens again to maintain sharp focus on that subject.

For many casual DSLR shooters, simply setting their camera to AI Servo AF and leaving it there when shooting action subjects may seem like all that’s necessary to get good pictures. And frankly, there are many instances where it is. The camera’s default settings when in AI Servo AF are engineered to provide good focus performance with a wide range of moving subjects, and even if you’re a critical shooter, you may find little to quibble with in your action images at these default settings.

But for some users, in some situations, you may find that adjustments to the camera’s AI Servo AF settings, to fine-tune the way continuous autofocus is performed, may get you even better results. Not long ago, any ability to go into a camera’s settings and change the way continuous AF was handled was strictly limited to absolute top-of-the-line, professional cameras. But today, at a very reasonable price point, we find that technology and flexibility has trickled-down to a popular priced camera like the EOS 80D.


What adjustments can be made to AI Servo AF?

These fall into four categories, and we’ll discuss each separately. Consider the general questions we ask about each initially (below) as you begin to wrap your mind around our discussion of AI Servo AF and potential adjustments:

1. If you’re focusing on a moving subject, how will the AF system respond if there’s a sudden change in what the camera is seeing?

This is the camera’s Tracking Sensitivity. Normally, the camera allows a small cushion of time to re-acquire your original subject if there’s a sudden interference or change — like a referee momentarily stepping between you and an athlete you’ve been focusing upon. Or, if you’re following a moving subject, and suddenly your AF point is on the background instead of that subject. You can tell the camera to allow even more time to re-acquire an initial subject, or conversely, command it to re-focus almost instantly on any new subject as it appears.

2. Should the AF system expect a steadily-moving subject, or expect one that will be changing speeds as you capture it?

This is the camera’s Accel./Decel. Tracking. When first introduced in high-end EOS models, this was a revolutionary control for AF… until that time, AF systems were factory-set to expect a given type of movement, and other types of movement were a bit of a compromise. Now, the EOS 80D allows tailoring the AI Servo AF to expect relatively steady movement (the factory-default setting), or can be adjusted in two stages to accommodate moving subjects that tend to change speeds, stop-start, and so on.

3. If you’re using a large area of AF points, how rapidly should the AF system change the active AF point(s) to continue to track a subject as it moves laterally across the frame?

This is AF Point Auto Switching. Think of it as a tool to fine-tune the AF system’s character if you’re using either the Automatic AF point select mode (all AF points active), or the Large Zone AF setting. Either way, there’s a large area of AF points that can view the subject… if/when that subject moves left-right, or up-down, the idea is that the Automatic AF point selection will let the system change AF points to continue to track the subject. The AF Point Auto Switching adjustment lets you define how rapidly it’ll change from the original point to a new location, as the subject moves.

4. When you press down fully on the shutter button, do you want the shutter to fire in the least amount of time, or do you want the camera to delay shutter firing, if necessary, to allow the AF system to insure sharpest possible focus?

This is AI Servo 1st (or 2nd) Image Priority. Two separate settings, allowing you to adjust the camera’s responsiveness during AI Servo AF. While fastest possible shutter firing time (least amount of “lag time”) sounds like a good thing, there will be times where the AF system hasn’t had time to sufficiently confirm sharpest focus. For images that won’t be significantly enlarged, or won’t be evaluated critically, this may not be a problem. But if sharpest focus is important, it can be desirable to slow the process down, and allow a little more time — when the AF system needs it — to ensure sharpest focus when the shutter is fired.

AI Servo 1st Image Priority:

If you quickly press fully on the shutter button, without a discernable half-press to begin focus a second or two earlier, you’re asking the camera to begin focus, drive the lens to the proper position, and fire the shutter almost simultaneously. While the AF system has a bit of a delay built-in to allow some time to properly AF, the camera has two user-controllable options.

- Focus Priority tells the camera to prioritize focusing, and if needed, slow down shutter firing for an initial shot (in AI Servo AF) to allow added time to nail the sharpest possible focus.

- Release Priority, on the other hand, tells the camera to prioritize the fastest possible shutter release timing. For situations where capturing split-second types of peak action are a key factor, you may want to try this setting, which can speed-up “lag time” (at the potential cost of truly sharp focus in some cases, with AI Servo AF).

AI Servo 2nd Image Priority:

Basically, if your Drive speed is set to continuous shooting, this tells the AF system — from the 2nd shot in a sequence onward — do we want to put priority on shooting at the fastest possible FPS frame rate, even if the AF system may not be able to fully keep up? Or, on the other hand, do we want the maximum number of sharply-focused frames we can get in a sequence, even if the camera needs to slow down the drive speed to achieve this?

- Speed Priority commands the system to shoot at the fastest possible FPS rate (the EOS 80D can shoot up to 7 fps), and still allow continuous AI Servo AF. But if the subject is challenging, the system is told to keep shooting even if the AF isn’t fully confirmed for each shot.

- Focus Priority, as you might expect, does the opposite: during high-speed continuous shooting, with AI Servo AF, the system is told that if necessary, the camera needs to slow down shooting speed to allow the AF system to get sharpest possible focus for each frame in a sequence, with moving subjects.


In the beginning: keep things simple!

It’s really easy for a new camera owner to jump right into the camera’s menu system, and start making this change and that change, before really even understanding how his or her camera’s AF system behaves in general. It’s easy to start over-thinking things. So for users who are just getting acclimated to these controls, our first suggestion is maybe the most important: keep it simple! If you’re shooting moving subjects, whether it’s your kids playing youth sports, a horse event at a local polo club, or birds in flight, start your journey by simply setting the AF system to AI Servo AF. Learn what its responses and results are, and the factory-default settings, for the types of action you’re shooting. Then, when you’re acclimated to its strengths and any possible weaknesses, you’re in a position to begin to systematically use the tools the camera offers to fine-tune your results.


Are these adjustments for AF the same as in the previous Canon EOS 70D?

Almost. EOS 80D adds one new AF option, which is AF Point Auto Switching. This changes the speed at which the AF system will change focus points to continue to cover a subject that moves left-right, or up-down around the frame. And, it only applies if you have a large active AF Area, such as the Automatic AF point selection, or Large Zone AF (with AI Servo AF active as well). Predictably, this setting is ignored when using just a single AF point.


Are these AF Adjustments the same as the “AF Cases” in high-end EOS cameras?

Essentially, yes. However, the EOS 80D (and previous EOS 70D) have no separate AF Menu tab, and don’t have the AF Configuration Tool menu (list of “cases”). Therefore, these AF adjustments are all handled individually on the 70D and 80D. The “cases” in recent high-end EOS models attempt to combine various combinations of these same settings, to tailor their AF systems to specific types of subject action and situations.


Applying these AI Servo AF adjustments in some real-world situations

OK, you’re at the point of wanting to further fine-tune the camera’s focus characteristics, with moving subjects and AI Servo AF. Let’s take a look at a few possible real-life action shooting scenarios that might cause some focus inconsistencies, and show how some of these adjustments might indeed help the camera produce even better results.

  • Moving subjects in low light, and/or with very plain detail
    These can cause any AF system to have trouble simply “seeing” the subject sufficiently, and thus being able to fully react to its movements. This could be anything from amateur sports in a dimly-lit school gym or night sports “under the lights,” to telephoto shots in sunlight of subjects with very plain detail.

- Switch to Focus Priority in both 1st and 2nd Image Priority settings Doing so tells the AF system to allow more time to assess what detail and subject information is present, and give a better chance of a higher percentage of sharp shots. Responsiveness and ultimate FPS shooting speed may drop, but the AF benefits may outweigh the performance “hit.”

Photo of a hockey player

Indoor sports, and especially night sports outdoors present the problem of low light. And, sometimes subjects have rather plain detail with little contrast or texture for the AF system to focus upon. By changing to “Focus Priority” in both the 1st Image Priority and especially the 2nd Image Priority settings, the AF system is instructed to take extra time if needed to insure positive and sharp focus. 2nd Image Priority applies to all shots in a continuous sequence, after the very first shot.


  • Fast-moving subjects which are hard to keep one AF point solidly upon
    One obvious example is birds in flight — always a popular subject among nature photography enthusiasts. But sports with unpredictable movement, ranging from soccer and US football to slalom skiing might fall in the same category. And, if the subjects are relatively small in the frame, this is underscored… it may be even harder to keep one AF point consistently upon a fast-moving subject.

- Change Tracking Sensitivity to “Locked On” setting This changes the AF system’s responsiveness, so that if and when you momentarily “lose” that fast-moving and sometimes small subject, the AF system won’t immediately try to re-focus on the background or whatever the AF system now sees. You’ve got a perceptible moment to put your active AF point(s) back on the original subject.

-Switch to Focus Priority for 2nd Image Prioritiy setting Again, this tells the AF system to allow a bit of extra time (only when it’s needed) to insure that focus is as crisply placed on a moving subject as possible.

-Consider switching to either Large Zone AF or Automatic AF point selection, and combine that with AF Point Auto Switching set to level 1 or 2 This isn’t always the right answer, but especially with a single moving subject (as opposed to multiple players on a field, or a flock of flying birds), this can very much minimize the importance of keeping one AF point on a challenging subject. Setting the AF Point Auto Switching to level 1 or 2 speeds-up the process of the larger AF Area changing the active AF point, to continue to track a subject if it leaves the initial picture area and needs other AF points to keep it in focus.

Photo of birds flying

Sometimes, it’s hard to keep one AF point consistently upon a moving subject — especially if it’s relatively small in the frame, and/or moving unpredictably. A couple of AI Servo AF adjustments can help here, primarily changing the Tracking Sensitivity to the “Locked On” setting. This means that if your AF point(s) momentarily lose the subject, like these birds, the AF system won’t immediately try to re-focus on the sky behind them.


  • Long telephoto lens shots of vehicles or athletes which are moving at relatively consistent speeds
    This could be anything from joggers to Olympic sprinters, or bicyclists in a park to Formula 1 race cars. The bottom line is you anticipate their movement and speed will tend to be relatively steady, you’re shooting as tight as you can with a telephoto lens, and they’re coming rather straight toward the camera — no sudden turns are likely.

-Accel./Decel Tracking at Zero This optimizes the AI Servo AF for relatively steady movement — whether it’s a race car or someone walking toward or away from the camera.

- If maximum number of shots is needed: AI Servo 1st / 2nd Image Priority to “Speed” First thing: the word “speed” does not mean that AF is faster or inherently better for moving subjects! But with a steadily-moving subject, which you assume you can readily keep your AF point(s) continually upon, the Speed option will give you fastest FPS operation. Think of a photographer shooting Track and Field events, for instance: he or she might have numerous opportunities to photograph runners in an event like the Mile or 1500 meter run; for the 100 meter sprints, you’ve basically got one pass to get your shots. Speed Priority, when all else is locked-down, will tell the camera to shoot at the fastest possible speed.

Photo of a cross country runner

Many moving subjects approach the camera at a steady rate of speed — regardless of whether it’s fast or slow. These are subjects that AI Servo AF will rarely have trouble with, as long as you keep the active AF point(s) reliably on part of the subject with good detail and contrast. When movement is predictable, you can ensure fastest continuous shooting by setting “Speed” priority for the 1st Image and especially 2nd Image Priority settings within the 80D’s Custom Functions menu.


  • Motorsports: vehicles either slowing down to enter a corner, or speeding up as they begin to exit a corner
    This is one example of subjects that change speeds. Anyone who’s driven or ridden in these situations knows how hard racers brake in the approach and early stages of cornering, and likewise, how hard they are on the gas as they exit a corner. Bottom line: vehicles change speeds, and this can sometimes throw off AI Servo AF.

- Accel./Decel. Tracking to level 1 or 2 This is huge, if your subjects are likely to change speeds. Level “zero” anticipates basically continuous, steady movement; boosting this sensitivity to 1 or 2 progressively re-tunes the AF to accommodate rapid changes in subject speed. Don’t assume you need to jump to Level 2; while the changes to AF character are sometimes subtle, you may find Level 1 is an acceptable adjustment.

- Tracking Sensitivity to “Responsive” This would have less of an impact, but it still tailors the AI Servo AF to respond quickly to sudden changes in what the AF point(s) are covering. For subjects that suddenly change speeds, this could give a little boost toward re-focusing with even less tendency to delay.

Photo of motorcycle

Changes in speed as a vehicle enters or exits a corner can throw-off some AF systems. By setting the EOS 80D’s Accel./Decel. Tracking to Level 1 or 2, you’re telling the AI Servo AF to expect changes like this motorcycle accelerating as it exits a corner.


  • Sports or wildlife where sudden changes in speed or direction are anticipated
    This can range from shooting sports like basketball from under the basket with a short focal length lens, to a wild animal park watering hole where predators may suddenly appear and cause other animals to quickly take evasive action. Another real-life example: sports like gymnastics floor exercises, where athletes will run and then suddenly stop or jump, and motorsports like motocross, where quick bursts on straightaways are punctuated by jumps, rough terrain, and sudden corners. In general, we mean action with a definite stop-start character to its movement.

- Accel./Decel. Tracking to Level 1 or 2 If there are really radical stops and starts, consider Level 2 — this optimizes AI Servo AF to assume there will be sudden speed changes, and upgrades its responsiveness to these changes.

- Tracking Sensitivity to “Locked On” Previously, we suggested leaving this on “Responsive,” if there was a good chance that the photographer can keep his or her AF point(s) continually on a subject. But if the nature of the movement is that unpredictable changes may happen, there may be breaks in the user’s ability to keep AF solidly on that subject. If you’re already focusing upon it, the “Locked On” setting tells the AF system to resist immediate changes if you suddenly lose a subject for a moment because it moved erratically.

Ballet dancer in action

Some moving subjects will tend to suddenly change speed and possibly leap or otherwise change direction as well. The EOS 80D’s AF system can be tailored to accommodate speed changes by setting Accel./Decel. Tracking from the default “zero” setting to Level 1 or 2. And, the AF can be instructed not to try to re-focus on something else if you momentarily lose the subject, by setting Tracking Sensitivity to “Locked On.”


  • Action situations — particularly with long telephoto lenses — where other objects or subjects may get in your way
    This is a real issue for sports photographers working on the sidelines. It’s incredibly easy to find referees or other athletes coming between you and the subject you’re trying to keep in focus, as it streaks toward you. The problem? AF may quickly try to re-focus on the new, unwanted subject, completely throwing your focus off, and mandating a somewhat lengthy few moments to re-acquire your initial subject after the interference is gone.

- Tracking Sensitivity to “Locked On” There are two levels of Locked On settings… either tells the AF system to resist re-focusing on that referee or other athlete, if it suddenly appears in your path and momentarily blocks your view of your initial moving subject. The same is true if a subject’s movement — especially with longer, heavier telephoto lenses — means that you may briefly have a hard time keeping the AF point consistently on your subject. (Think of a baseball photographer focusing on an outfielder trying to make a diving catch. There may be instances where it’s hard to keep that AF point or Area steadily on that subject as he or she runs toward the wall or rushes forward to dive for a sinking line drive.) Either way, Locked On means the AF will hold onto an initial subject longer, and resist sudden focus changes.

Soccer goalie in action

A common problem when shooting distant sports action with long tele lenses is the possibility of momentary interference from other athletes or referees. Switching the AF system’s Tracking Sensitivity to “Locked On” tells the AF system to pause in situations like this, and resist re-focusing on a new subject that suddenly enters the active AF point area.